Pressure sensing devices have become ubiquitous the past few years as they have found their way into many types of products. Utilized in automotive, industrial, consumer, and medical products, the demand for pressure sensing devices has skyrocketed and shows no signs of abating.
Pressure sensing devices may include pressure sensors as well as other components. Pressure sensors may typically include a diaphragm or membrane. Typically, this membrane is formed by creating the Wheatstone bridge in a silicon wafer, then etching away the silicon from the opposite surface until a thin layer of silicon is formed beneath the Wheatstone bridge. The thin layer is a membrane that may be surrounded by a thicker, non-etched silicon water portion forming a frame. When a pressure sensor in a pressure sensing device experiences a pressure, the membrane may respond by changing shape. This change in shape causes one or more characteristics of electronic components on the membrane to change. These changing characteristics can be measured, and from these measurements, the pressure can be determined.
Often, the electronic components are resistors that are configured as a Wheatstone bridge located on the membrane. As the membrane distorts under pressure, the resistance of the resistors also changes. This change results in an output of the Wheatstone bridge. This change can be measured through wires or leads attached to the resistors.
In some applications, it is particularly important that a pressure sensor have a specific form factor. For example, in many medical applications, it may be important that the pressure sensor be small, or have a thin form factor, or both.
But pressure sensors having such small form-factors may be difficult to manufacture. For example, these pressure sensors may be too small to use in traditional semiconductor assembly tools for wire bonding or flip-chip assembly. In some cases, the end product itself may be too small to accept pressure sensors mounted in standard semiconductor packages. If a pressure sensor needs to fit inside a small catheter, for example, it may not be possible to employ standard semiconductor packaging and assembly techniques.
Thus, what are needed are pressure sensors with features designed to improve manufacturability, where the pressure sensors have a small, thin form factor that may be readily manufactured and the method of manufacturing may improve yield and reduce overall costs.